Duplex S32205 & UNS S31803 Stainless Steel Pipe

ASTM A347/347H Stainless Steel Pipe

April 23, 2024

S31803 is the Unified Numbering System (UNS) designation for the original duplex stainless steel. The UNS system was created by a number of trade groups working together in the 1970’s, to reduce confusion from the same alloy being called different things or vice-versa. Each metal is indicated by a letter followed by five numbers, where the letter indicates the family of metals i.e. S for stainless steels.

In the world of stainless steel, Duplex 2205 stands out as a nitrogen-enhanced duplex alloy that tackles the common corrosion issues faced by the 300 series stainless steels. Unlike the fully austenitic 304 stainless or purely ferritic 430 stainless, Duplex stainless steels strike a balance between the two. The structure of 2205 duplex stainless steel comprises austenite pools surrounded by a continuous ferrite phase. In its annealed state, 2205 typically contains around 40-50% ferrite. Renowned as the workhorse grade, 2205 is the most widely used grade within the duplex family of stainless steels.

The UNS S31803 (ASTM F51) specification has largely been replaced by UNS S32205 (1.4462, ASTM F60). This reflected their desire to maximise the corrosion performance of the alloy, aided by the development of the AOD steelmaking process that allowed tighter control of composition. In addition, it also allowed the level of nitrogen additions to be influenced, rather than just present as a background element. Therefore, the highest performing duplex grade sought to maximise the levels of chromium (Cr), molybdenum (Mo) and nitrogen (N).

An Overview of 2205 Duplex Stainless Steel

The duplex structure of 2205 stainless steel offers a unique advantage by combining the favorable characteristics of ferritic alloys (such as stress corrosion cracking resistance and high strength) with those of austenitic alloys (including ease of fabrication and corrosion resistance).

It is important to note that the usage of 2205 duplex stainless steel should be limited to temperatures below 600°F (316°C). Prolonged exposure to elevated temperatures can lead to embrittlement of the material.

Chemical Composition, %

Cr	Ni	Mo	C	N	Mn	Si	P	S	Fe
22.0-23.0	4.50-6.50	3.00-3.50	.030 Max	0.14-0.20	2.00 Max	1.00 Max	.030 Max	.020 Max	Balance

ASTM Specifications

Pipe Smls	Pipe Welded	Tube Smls	Tube Welded	Sheet/Plate	Bar	Flanges, Fittings & Valves
A790	A790	A789	A789	A240	A276	A182

Mechanical Properties

Specified Tensile Properties ASTM A240

Ultimate Tensile Strength, ksi Minimum	.2% Yield Strength, ksi Minimum	Hardness Max.
95	65	31 Rockwell C

Mechanical Properties of UNS S31803

Tensile Strength,min.	Yield Strength,min.	Elongation,min.	Hardness Brinell, max
Mpa	Mpa	%	HB
620	450	25	290

Physical Properties of UNS S31803

Density	Thermal Expansion	Modulus of Elasticity	Thermal Conductivity	Electrical Resistivity
g/cm3	K	Gpa	W/m.k	Ω.m
7.805	13.7*10-6	200	19.0	0.085*10-6

What is UNS S31803?

Stainless Duplex S31803 material is widely used in chemical industries, marine tools and equipment, water desalination plants, food sector, paper and pulp industry and much more applications.

Temperature Range Of UNS S31803

Grade	Temperature
UNS S31803	1020-1100°C/ 1868-2012°F

Astm A790 UNS S31803 Specification

Grade	UNS	Duplex Industry Specifications
SAF 2205® 22Cr	UNS S31803	ASME SA-182 (F51), SA-240, SA-798, SA-790, SA-815 ASTM A182 (F51),A240, A276, A479, A789, A790, A815, A928, A988 SAE J405

Duplex Stainless Steel UNS S31803 Equivalent

Duplex 2205

UNS S31803

1.4462

F51

UNS S31803 Thermal Conductivity

Properties	Metric	Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F)	13.7 µm/m°C	7.60 µin/in°F

Duplex UNS S31803 Properties

Properties	Imperial	Metric
Duplex Steel S31803 Material Density	0.283 lb/in³	7.82 g/cm³

Corrosion Resistance

One of the key advantages of 2205 duplex stainless steel is its exceptional corrosion resistance, making it a cost-effective solution for numerous applications where the 300 series stainless steels are susceptible to chloride stress corrosion cracking. Stress corrosion cracking occurs when stainless steels are subjected to tensile stress while in contact with chloride-containing solutions. Moreover, higher temperatures further increase the susceptibility of stainless steels to stress corrosion cracking.

The combination of chromium, molybdenum, and nitrogen in 2205 imparts excellent resistance to chloride pitting and crevice corrosion. This resistance is particularly crucial in environments such as marine settings, brackish water conditions, bleaching operations, closed-loop water systems, and certain food processing applications. With its high chromium, molybdenum, and nitrogen content, 2205 offers superior corrosion resistance compared to common stainless steels like 316L and 317L in most environments.
Duplex S32205 and UNS S31803 are both types of stainless steel pipes that belong to the duplex stainless steel family. These alloys are highly sought after in various industries due to their exceptional combination of mechanical strength and corrosion resistance. Let’s delve deeper into the features and applications of Duplex S32205 and UNS S31803 stainless steel pipes.

1. Chemical Composition: Duplex S32205 and UNS S31803 stainless steel pipes have a similar chemical composition. They are both duplex alloys, consisting of approximately 22% chromium, 5-6% nickel, 3% molybdenum, and a small amount of other elements such as nitrogen and manganese. This composition provides excellent resistance to corrosion and enhances the overall strength of the pipes.

2. Duplex Structure: The term “duplex” refers to the dual-phase microstructure of these stainless steel pipes. They consist of an equal mixture of austenite and ferrite phases, which contributes to their unique properties. The duplex structure provides increased strength, improved resistance to stress corrosion cracking, and enhanced toughness compared to conventional austenitic stainless steels.

3. Corrosion Resistance: Duplex S32205 and UNS S31803 stainless steel pipes exhibit excellent resistance to various types of corrosion, including pitting, crevice corrosion, and general corrosion. This makes them suitable for applications in aggressive environments such as marine, chemical, and oil and gas industries.

4. Mechanical Properties: Both Duplex S32205 and UNS S31803 stainless steel pipes offer impressive mechanical properties. They have high tensile strength, which allows them to withstand heavy loads and pressure. Additionally, these alloys have good ductility and impact strength, making them suitable for demanding applications.

5. Applications: Duplex S32205 and UNS S31803 stainless steel pipes find extensive use in a wide range of industries. Some common applications include:

Oil and gas exploration and production: These alloys are used in offshore platforms, subsea pipelines, and oil refineries due to their resistance to corrosion in seawater and harsh environments.
Chemical processing: Duplex stainless steel pipes are employed in chemical plants and reactors where resistance to corrosive chemicals is crucial.
Desalination plants: The high corrosion resistance of Duplex S32205 and UNS S31803 makes them ideal for use in desalination plants, where they come into contact with highly saline water.
Structural and architectural applications: These stainless steel pipes are utilized in structural components, bridges, and architectural designs due to their strength and aesthetic appeal.

In summary, Duplex S32205 and UNS S31803 stainless steel pipes offer a unique combination of mechanical strength and corrosion resistance. Their duplex structure, chemical composition, and exceptional properties make them a preferred choice for various industries. Whether it’s for oil and gas, chemical processing, or structural applications, these stainless steel pipes provide reliable performance and durability.

For more detailed information on Duplex S32205 and UNS S31803 stainless steel pipes, please visit link.

FAQ

What is the difference between Duplex S32205 and UNS S31803 stainless steel pipes?
Duplex S32205 and UNS S31803 stainless steel pipes have similar chemical compositions and properties. They are essentially the same alloy, with slight variations in their manufacturing standards and designations.
What are the advantages of using duplex stainless steel pipes?
Duplex stainless steel pipes offer a combination of high strength, excellent corrosion resistance, and good toughness. They are particularly useful in aggressive environments where both strength and resistance to corrosion are required.
Can Duplex S32205 and UNS S31803 stainless steel pipes be welded?
Yes, these stainless steel pipes can be welded using appropriate welding techniques. However, it is essential to follow proper procedures to maintain the corrosion resistance and mechanical properties of the pipes.
Are Duplex S32205 and UNS S31803 stainless steel pipes suitable for high-temperature applications?
Yes, these stainless steel pipes can withstand moderately high temperatures. However, it is important to consider the specific application and consult with experts to ensure the suitability of the alloy for the intended temperature range.
Where can I find more information about Duplex S32205 and UNS S31803 stainless steel pipes?
For more detailed information on Duplex S32205 and UNS S31803 stainless steel pipes, including specifications, applications, and technical data, please visit link.